Found a white dwarf that "takes" the energy of a normal star

Analyzing data from the Spektr-RG (SRG) spacecraft and NASA’s satellite for studying transit

Exoplanet Survey (TESS), astronomers have discovered a magnetic cataclysmic variable. The new object was named SRGE J075818-612027. He most likely belongs to the polar subtype.

Cataclysmic variablesvariables, CV) are binary star systems that consist of a white dwarf accreting material from a normal stellar companion. Cataclysmic variables are stars whose brightness non-periodically increases many times, after which it decreases to the level of a quiet state. And polars are a subclass of cataclysmic variables that differ from other CVs by the presence of a very strong magnetic field in their white dwarfs.

Recently, a group of astronomers led by SametOka from the Leibniz Institute for Astrophysics Potsdam (AIP) in Germany analyzed observations of the field of the open cluster NGC 2516 using the eROSITA Spektr-RG X-ray telescope and TESS and discovered a new CV.

X-ray image of NGC 2516 obtained by eROSITA. The white dotted circle marks the position of SRGE J075818-612027. Photo: Ok et al, 2023

SRGE J075818-612027 was identified as one of the brightest X-ray field objects during the eROSITA Calibration and Performance Verification (CalPV) observing phase.

Further observations of SRGE J075818-612027 revealed its variability with a period of about 106 minutes. It is also a magnetic cataclysmic variable.

According to the study, the X-ray spectrum of SRGEJ075818-612027 is compatible with single-temperature thermal plasma radiation at levels around 10 keV, which is typical for polars. In addition, the object exhibits large differences in magnitudes over long time scales in both optical and x-ray wavelengths. This behavior can be interpreted as high and low states, which also supports its classification.

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Cover photo: NARA & DVIDS Public Domain Archive